Gaster Sans
by Wolfbeware
Summary: Gaster!Sans. Slice of life for the first part. Afterwards, the plot starts to kick in the story.
1. A Smoke Break

He felt the snow crush under his sneakers. It felt strangely familiar to him. Even though he was in a very different place, it felt a little like home. New York City, the tallest city you could ever live in America. It felt fitting to him and his brother, with tall buildings, lots of jobs, fun events.

Sans walked across the small balcony. Snow crushed under every step. He took out a cigarette from his jacket pocket. "Finally," he said, not realizing he has said it aloud.

With a flick of a lighter, his cigarette was ablaze. He leaned his body weight into the railings to look down. He was on the 70th floor. What a wonderful floor number to be on. He and Papyrus liked to call this place home.

Sans was finally happy that he was free. Free from all the worries that the past has given him. Free from all of the experiments. Free from his father, although they may be stuck together for the rest of his life.

Sans stood up straight. He sighed at the thought he would never truly become free from his father and all of their workings. Strange enough as it sounds, Sans began to work a full-time job as a scientist. His love for science did not go away after moving to the surface. He was happy about that, more money the better the job.

He looked around, pulling his smoke from his jaw. However, he did not blow out the smoke. The smoke seemed to come out of his eye sockets and his jaw on its own. When in the street, every human around gave him a weird glare when that had happened. Sans was never sure the reason, though. It was normal for him. He is a skeleton, after all.

Putting the cigarette back into his jaw, he noticed something different in the air. It was not smoke. It was something else.

It was his magic. It was in the air floating like fog around his skull. He turned around, looking through the glass door. He saw his brother looking at him. Papyrus seemed to be smirking.

Papyrus, who was also fused with their father, knew that Sans had too much magic to contain his small body. Usually, it was shown with a thick layer of it surrounding his body, but since the change it has been burned with the smoke.

Sans looked at the yellow fused air in interest. He always thought it was curious to have to "burn" magic. Though, he's been able to show his skeletal body in public more often than not. He almost always had not had a shirt on. All he had on was a jacket and a pair of jeans. He knew some of the new human laws they had to go by, but not all of them. He had to find out all of them before he could do whatever he wanted. The last thing he wants is to be arrested in the human world.

Papyrus was cooking dinner. Steadily stirring the homemade pasta, he was smiling. His brother had finally accepted the change of place and scenery. Papyrus' turtleneck sweater was warming him. Papyrus turned around, once more.

Sans stood there. He did not notice Papyrus was looking at him, and instead looked out into the distance. The city was strangely still. Pretty much all the humans knew that the monsters came from the underground to have peaceful lives on the surface, but ignored the fact that they were human. Humane. Civilized. The only difference between humans and monsters was their forms and souls.

Sans suddenly felt a magical fire in his left eye. It hurt, but it always did. This time was worse than a lot of times, but it did not change his movements.

Pain. Harm. Terror. The three things only his father gave him before they fused. He wanted to escape from. He wanted to go as far away from his father as he could.

His cigarette dropped to the ground. It had been fully smoked. No point in a smoke with no smoke left in it. He turned around to see his brother putting the spaghetti he had just made onto a large plate.

Sans stepped into the cigarette and rubbed it on the ground of the balcony so that nothing would catch fire. Sans opened the glass door. With a large sigh of relief, he sat down. His brother smiling as he did so. They both smiled at each other.

This is how it was supposed to be.


	2. A Visit

I walk into the large house. It felt friendly and happy. As if someone called this place "home." I wish I could say the same about my apartment in New York. I sigh at the thought that the surface might never be able to be "home."

The human, Frisk, seems very happy to see me. I guess they still remember me as the Sans I used to be. I force a smile. I was scared of coming here. I refused the first time Frisk offered, but they eventually got me to come over here.

"Hi, Sans!" they say very happily.

"Hey, kiddo," I respond as I pat their head.

Frisk was now seventeen, but that didn't mean they were still shorter than me. The fusion made me 5 feet and 6 inches. That was probably the only benefit from all this. I look around. I know Toriel should be here. If she isn't, then what's this kid planning?

"So, um, where's your mom?" I ask still looking around.

"Well, um, she went out. To, um, buy some groceries! She knows that your diet is much different than our's so she's getting more food," they say nervously.

They were lying. I could hear it in their voice. They apparently don't lie often. That's probably a good thing for Toriel. I continue to walk around the house. Frisk said I could stay the night. I smirk. This is an interesting experience. A teenager sneaking in their uncle into their mother's house.

"So, what ya planning?" I ask, hoping they would give me a truthful answer.

After a few seconds of nervous laughter, they say, "What are you talking about? I'm not planning anything!"

"Oh, sure. You let me in when your mother is away, and you're lying like there isn't a tomorrow," I say with a slightly more genuine smile.

"Fine, I want you to scare her!" they say a bit too excitedly.

I guess they don't do this very often. "Ya got anyone else on the prank?" I ask just so that we could plan it a bit better.

"Well, Papyrus, and a few friends of mine. They should be arriving soon," They respond, finally truthfully.

"So, where exactly is your mom?" I say looking straight at them.

They return the stare back with saying, "Um, the, uh, airport," nervously.

"What's she doin' there?" I ask, now only out of curiosity and concern.

I close my eye sockets and rub the start of the bridge of my nose. This is probably the worst thing this kid has ever done. They are wearing a striped T-shirt and some tight skinny jeans. I take my hand off my skull and lean on the counter.

I made a grunting sound, as the pain hit me. It wasn't that bad this time, but it sure did mess up what I was doing.

"Sans, are you okay?" Frisk asks after I started walking over to the couch.

"Yeah, I'll be fine," I respond in between my gasps for air.

As I walk slowly to the couch, I notice from the corner of my eye, the great concern of the teenager. Once I got near the couch, I let my body fall onto the soft cushions. Now laying down, I try my best to breathe deeply and smoothly. I failed, with my breathing fast and unsteady.

My jacket felt heavy. I decided to wear a turtleneck shirt that I bought a few months ago today, so Toriel or Frisk wouldn't have to feel awkward. I regret this fact. My shirt was overwhelming. It was crushing my rib cage. A low rumble of pain came out of my jaw.

"You don't sound ok, Sans. What's wrong?" Frisk asks as they carefully walk next to the couch.

"This happens a lot more often than what you'd think, Frisk. I'll be fine," I somehow get out of my jaw.

I had aches everywhere. Head to toe. It all hurt. Thank goodness for this soft couch. My feet were off the edge of the couch, so I didn't dirty the couch. I sigh.

"Do you need anything?" Frisk asks kindly as their concern runs throughout their veins.

"Maybe a blanket. This one might last a while," I say, making sure that I didn't have direct eye contact with them.

Frisk hurriedly left the room. I just laid there, comfortably. I turn over so that my body could be on my back. My feet were still off the couch. Finally, my breathing settled to a nice deep and filling pattern.

Frisk came back with 3 blankets, and says, "Will this be enough?"

I turn my head to look at them. "Yes, thank you, but I have a strange favor to ask you: could you please take off my shoes? I don't want your couch to get dirty," I say knowing that if I did move the pains would become worse.

Frisk only just walked over to me. They placed the 3 blankets on top of me that covered my whole body except for my shoes. Afterwards, they walk to the end of the couch that had my shoes and took them off.

They did not mess around. They knew that I had to rest. I guess I don't have a good excuse to move. I eventually fell asleep.

I was suddenly awakened by the sound of a shriek. It was Toriel. She drops the bag of souvenirs. I hear a crack from something in the bag, as my eye sockets slowly open up. Half of my face was covered by a blanket. "Hello, Toriel," I say nervously, sure that Frisk did not tell her that I was here yet.

"Oh my goodness, Sans. What are you doing here?" she almost immediately responds.

Most of the aching pains were gone, so I sat up. Most of the blankets that were on top of me fell off onto my legs. I smirk," Your kid invited me. They wanted to prank you. I'm so proud of them."

Toriel giggles," Well, I'm glad that you are here. Me, Undyne and Alphys are going out tomorrow. Would you like to come? I'd think they'd like to see an old friend again."

I rub the back of my neck, as I stand up. "Sure, why not? I might as well," I respond.

"Good! Anyways could you possibly know where my child has gone?" she asks, probably wondering if she should scold Frisk for trying to prank her.

"Nope. Been sleeping here for," I look at the clock, "three hours."

"Oh, Sans, you are exactly the same as before," she smiled and patted my head, before leaving the room to go search the rest of her house.

I sigh as if that were true.


	3. A Girls' Night Out

"Hey, Alphys and Undyne!" Toriel yelled from the opposite end of the restaurant.

Toriel and Sans were in a large corner booth near the back of the restaurant. Sans was in a black suit that Frisk told them to bring. Sans knew what Frisk was planning, but that plan failed a long time ago. Toriel was wearing a sleeveless purple sparkly dress, that wasn't too short.

Sans looked over to where Alphys and Undyne were worriedly. What if they didn't like him? It's been too long. Sans has changed so much compared to back then. When he was normal.

Undyne and Alphys walked over quickly excitedly, or at least Undyne was. Alphys looked nervously at Sans as she walked over.

"Hey, Tori!" Undyne yelled back before sitting down next to her.

Toriel looked at her happily, while Sans looked at the couple nervously. "H-hey there," Sans somehow got out his jaw despite his jaw was shaking as he spoke.

"Hey S-Sans," Alphys said to Sans only a little less nervous than he was.

Sans smiled, even though it wasn't genuine. He knew that Alphys was worried about him. He's known Alphys for long enough to understand her expressions.

Sans shrugged it off, as Toriel scooted more towards him to let Alphys sit down. Toriel smiled at the cute couple in joy. "So, I haven't seen you two in a while, how are you? What have you been doing? Anything new?" she said with a bright smile that almost brightened Sans.

"Well, nothing re-" Alphys started to say nervously, before being cut off my Undyne.

She excitedly said," We're getting married next summer!"

Sans thought it was pretty obvious who proposed, so he decided not to ask. Toriel giggled at the two. However, Sans face changed back to his relaxed status, before looking around nervously trying to find anything else he could focus on that wasn't the three monsters next to him.

"Hey, Sans, I haven't seen you in what? Seven years?" Undyne said after noticing that Sans was looking around the restaurant," What you've been doing?"

Sans slowly moved his head towards Undyne. He sighed. "I took a scientist job," he said not knowing what other to say.

"You? A scientist? That has to do work? I very much doubt that," Undyne responded with a smirk.

Sans sighed, and rested his head on his right arm," I changed, Undyne. If you couldn't tell already."

A spear appeared in Undyne's right hand, before she said," Who the hell are you?"

"U-Undyne, I-I'm Sans! What are you-" Sans tried to get out his jaw before the spear sharply hit his chest.

"WHERE IS SANS?!" Undyne demanded, jumping on top of the table.

"Undyne," Toriel stared at Undyne on top of the table with harsh eyes," Sit down."

Undyne and Sans looked at her, then back at each other. As Undyne slowly crawled back to her side of the table, her dress seemed to tighten around her. Everyone in the restaurant stared at the small booth of monsters. Sans began to hope that they'd get kicked out, so he could be out of this conversation.

"We don't want to be kicked out, Undyne," Toriel stated, which made Sans sweat a bit.

Undyne looked at Toriel nervously. Sans tried his best to look away from Undyne, but his eye started to light up with his yellow magic. He put his skeletal hand on his left eye, even though he knew it would go straight through his hand anyway.

"Sans? Are you okay?" Alphys said noticing the air around Sans becoming a deep yellow color.

Sans was looking at Toriel nervously, before answering," I'm alright, I guess."

"What happened to you?" Alphys said nervously," I-if you don't mind me a-asking."

"Well, um," Sans started to say before pausing trying to look for a good reasonable answer.

A moment of silence fell upon the table.

Each one of them running through their own mind.

"Where's Sans?"

"Why did Undyne try to do that to her friend?"

"What do I do?"

"How did the fusion happen?"

A phone ring lifted the silence. It was Toriel's. "Sorry, but I must take this. It's Frisk, excuse me," she said before Sans got up to let her leave the booth.

She left while picking up the phone," Hello? This is Toriel,"

"It happened right after monsters left the underground," Sans said trying to continue the conversation.

"What happened, Sans?" Undyne asked gritting her teeth a bit.

Sans sighed. "This," he said taking his hand off his left eye.

Undyne smirked," What the he-"

"Sans, how did you change your magic color?" Alphys questioned, but accidentally cut off Undyne.

Undyne's back became straight as she remembered his magic used to be blue. "Wait, monster's can change there magic?" she asked now also curious.

"No, they can't Undyne, but there is an exception. If a monster fuses with another monster then their magic can change based off the colors of each monster. It is very rare for two monsters to fuse however. Each would have to be willing to do it, and over 70 percent of the time it fails," Alphys said trying to explain to Undyne.

"Ok, but Sans obviously looks different, so can't we just assume that he did that?" Undyne said in response pulling her arms up to gesture at Sans' different form, but then immediately set them down to let Alphys talk.

"Yes, but Undyne. If he willingly fused with someone, don't you think that he'd, you know, tell someone about it?" Alphys said a bit nervously.

Undyne shifted her head towards Sans, her old friend, then back at Alphys. Undyne sighed. "Well, I guess so," her vision moved back towards Sans," What happened to you?"

"Well, a little after we left the Underground," Sans began.


End file.
